1. Field of the Invention
The present invention relates to a display element making use of the electrowetting phenomenon and a display device having it.
2. Related Background Art
Liquid crystal display elements are commonly used as conventional display elements. Many liquid crystal display elements are constructed of twisted nematic type liquid crystal cells having the twist angle of 90xc2x0 and in such structure as to change the twist condition of liquid crystal molecules according to a state of an electric field placed between transparent electrode substrates to affect a state of polarization of transmitted light and to control transmission/non-transmission of light through a polarizer, thereby implementing display of image information.
There are also some proposals of display methods making use of scattering of light. As display elements making use of scattering of light, there are known display elements utilizing dispersion-type liquid crystals in which liquid crystals are dispersed in polymer; for example, National Publication of Translated Version of Japanese Patent Application No. 58-501631 (corresponding to U.S. Pat. No. 4,435,047) discloses NCAP film and National Publication of Translated Version of Japanese Patent Application No. 63-501512 (corresponding to U.S. Pat. No. 4,688,900) discloses PDLC film.
On the other hand, the electrowetting phenomenon (also called electrocapillarity) is known as a phenomenon in which interfacial tension varies with application of a voltage to a liquid to cause migration or deformation of an interface. This electrowetting phenomenon will be described referring to FIGS. 5A and 5B.
In FIGS. 5A and 5B, reference numeral 501 designates a substrate electrode, 502 an insulating layer formed on the substrate electrode 501, and 503 an electroconductive liquid droplet. FIG. 5A shows a state in which no voltage is applied between the substrate electrode 501 and the droplet 503 (V=0). When a voltage (V=V0) is applied between the substrate electrode 501 and the droplet 503, as illustrated in FIG. 5B, a kind of capacitor is formed to accumulate electrostatic energy. This electrostatic energy changes the balance of surface tension of the droplet 503, whereby the shape of the droplet 503 is altered from the state of FIG. 5A in which no voltage is applied.
This electrowetting phenomenon described above is utilized in the varifocal lens disclosed in WO99/18456 and in the electrocapillary display sheet disclosed in Japanese Patent Application Laid-Open No. 9-311643.
An object of the present invention is to provide a display element of novel structure making use of the electrowetting phenomenon described above and a display device having it.
A display element of the present invention for accomplishing the above object is a display element comprising a plurality of pixels and constructed to display image information by modulating light passing through each pixel, said display element comprising the following for each of the pixels:
a mask having a shield portion in part; and
a first fluid and an electroconductive or polar, second fluid being immiscible with each other,
wherein an amount of light passing through said mask is regulated in such a way that a voltage applied to said second fluid of each pixel is varied to alter the shape of an interface between said first fluid and said second fluid, so as to increase or decrease light incident to the shield portion of said mask.
A display device of the present invention comprises a light source, the display element of the present invention described above, and lightguide means for guiding light from the light source to the display element.